Fig. 1.

Schematic representation of a hypothetical mechanism for discogenic low back pain. An anular rupture causes exposure of the nucleus pulposus to the outer annulus fibrosus, which may induce nerve injury and nerve ingrowth into the disc. Under inflammatory conditions, nerve growth factor (NGF) is induced in the disc and acts on the dorsal root ganglion (DRG) neurons through the peripheral terminals in the disc. Disc-innervating DRG neurons have a high sensitivity to NGF. Therefore, NGF may promote nerve ingrowth into the disc, sensitize DRG neurons, and cause neuronal sprouting into the dorsal horn. Our recent studies demonstrated the possibility that anti-NGF treatment or fusion surgery can resolve these pathological conditions related to the generation of discogenic pain